• 대한화학회지
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• 제63권2호
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• pp.94-101
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• 2019

Nb, Mo-doped and Nb/Mo-codoped $VO_2(M)$ nanocrystallites with various doping levels were synthesized for the first time by a hydrothermal and post thermal transformation method. The reversible phase transition characteristics of those doped $VO_2(M)$ was comparatively investigated. Nb-doping of $VO_2(M)$ by this method resulted in a very efficient lowering of the transition temperature ($T_c$) with a rate of $-16.7^{\circ}C/at.%$ that is comparable to W-doping, while Mo-doping did not give a serious reduction of $T_c$ with only a rate of $-5.1^{\circ}C/at.%$. Nb/Mo-codoping gave a similar result to Nb-doping without a noticeable difference. The thin films of Nb-doped and Nb/Mo-codoped $VO_2(M)$ with a thickness of ca. 120 nm were prepared by a wet-coating of the nanoparticle-dispersed solutions. Those films showed a good thermochromic modulation of near infrared radiation with 30-35% for Nb-doped $VO_2(M)$ and 37-40% for Nb/Mo-codoped ones. Nb/Mo-codoped $VO_2(M)$ film showed slightly enhanced thermochromic performance compared with Nb-doped $VO_2(M)$ film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.378.1-378.1
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• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.288-288
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• 2012

In this study, we investigated that the resistance switching characteristics of W-doped NbOx films with increasing W doping concentration. The W-doped NbOx based ReRAM devices with a TiN/W-doped NbOx/Pt/Ti/SiO2 were fabricated on Si substrates. The 50 nm thick W-doped NbOx films were deposited by reactive dc magnetron co-sputtering at $400^{\circ}C$ and oxygen partial pressure of 35%. Micro-structure of W-doped NbOx films and atomic concentration were investigated by XRD, TEM and XPS, respectively. The W-doped NbOx films showed set/reset resistance switching behavior at various W doping concentrations. The process voltage of set/reset is decreased and whereas the initial current level is increased with increasing W doping concentration in NbOx films. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of metallic tungsten of oxygen of W-doped NbOx.

• 한국전기전자재료학회논문지
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• 제16권11호
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• pp.987-993
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• 2003

We fabricated thick film monopole antennas using Mo-doped BiNbO$_4$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped BiNbO$_4$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of Bi$_2$MoO$_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at.%, highest gain of -0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.300-304
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• 2002

We fabricated thick film monopole antennas using Mo-doped $BiNbO_{4}$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped $BiNbO_{4}$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of $Bi_{2}MoO_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at%, highest gain of ~0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

• Corrosion Science and Technology
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• 제22권6호
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• pp.408-418
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• 2023

In this study, we synthesized and characterized garnet-type Li_7-xAl_xLa₃Zr_2-(5/4)yNbyO₁₂ (LALZN) solid electrolytes for all-solid-state battery applications. Our novel approach focused on enhancing ionic conductivity, which is crucial for battery efficiency. A systematic examination found that co-doping with Al and Nb significantly improved this conductivity. Al³⁺ and Nb⁵⁺ ions were incorporated at Li⁺ and Zr⁴⁺ sites, respectively. This doping resulted in LALZN electrolytes with optimized properties, most notably enhanced ionic conductivity. An optimized mixture with 0.25 mol each of Al and Nb dopants achieved a peak conductivity of 1.32 × 10^-4 S cm^-1. We fabricated symmetric cells using these electrolytes and observed excellent charge-discharge profiles and remarkable cycling longevity, demonstrating the potential for long-term application in battery systems. The garnet-type LALZN solid electrolytes, with their high ionic conductivity and stability, show great potential for enhancing the performance of all-solid-state batteries. This study not only advances the understanding of effective doping strategies but also underscores the practical applicability of the LALZN system in modern energy storage solutions.

• 한국결정성장학회지
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• 제8권3호
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• pp.401-406
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• 1998

LiNbO_3$ 단결정의 광학소자 광도파관 등의 응용을 위하여는 빛의 조사에 따라 굴절률이 변하는 광손상을 극복하여야 한다. 이러한 광손상 극복은 LiNbO_3$ 에 MgO를 첨가한 단결정의 성장과 산처리를 통하여 가능하다. 본 연구에서는 LiNbO_3$ 의 광손상 극복 기구를 이해하기 위하여, FT-IR을 이용하여 LiNbO_3$ 단결정에 MgO 첨가와 산처리가 발생시키는 격자결함의 변화를 OH- 흡수밴드를 통하여 간접적으로 관찰하였다. 또한 액체 헬륨을 이용한 온도강하시 생기는 격자결함의 관찰과 산처리한 시편의 광택연마와 열처리에 따른 격자결함으 조사하였다. MgO 첨가는 LiNbO_3$ 격자내 $Mg_{Nb}^{2+}$ 결함을 발생시켜 광손상 저항을 증가시키며, 산처리는 결정표면의 산소층에 $H^+$이온이 침입하여 격자결함을 발생시키며, 이 격자결함은 $400^{\circ}C$이상에서 열처리하면 $H^+$가 결정내부로 확산하여 들어감을 확인하였다.

• 한국결정성장학회지
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• 제30권5호
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• pp.194-199
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• 2020

2차원 층상결정구조를 갖는 금속산화물 나노시트의 조성을 제어함으로써 재료 물성 및 응용의 확장이 가능하다. 본 연구에서 니오비움(Nb)이 도핑 된 타이타늄산화물(TiO_y) 나노시트 합성에 성공함으로써 나노시트의 조성을 순수조성에서 도핑조성으로 확장할 수 있었다. 상세하게는 출발 물질인 층상 구조 금속산화물 합성 시 도핑 조성을 설계(K_0.8Ti_1.73-xNb_xLi_0.27O₄, x = 0, 0.03, 0.07)하고 고상 합성한 후 유기물처리를 통한 화학적 박리를 수행하였다. 이렇게 함으로써 니오비움이 도핑 된 타이타늄산화물 초박막 나노시트를 수득할 수 있었다. 나노시트의 크기는 x-y 방향에서 긴 길이 기준으로 2 ㎛ 이하였으며 두께(z 방향)는 약 1 nm였다. 니오비움의 도핑 여부는 XRD 및 SEM-EDS 분석을 통해 확인할 수 있었다.

• 한국결정성장학회지
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• 제5권1호
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• pp.1-10
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• 1995

CZ법을 이용하여 합치용융조성(congruent) $LiNbO_3$ 및 광손상에 큰 저항성을 보이는 $LiNbO_3$ : Mg 단결정에 MgO 첨가량을 2, 5 및 7 mol%로 변화시키면서 육성하여, 보상 방법으로 광손상을 측정하였다. 5 mol% 이상의 MgO 첨가시 광흡수단 및 $OH^-$ 흡수밴드의 특성이 크게 변화함을 관찰함으로써 MgO 첨가량에 일정한 역치(threshold)가 존재함을 확인하였다. $LiNbO_3$ : Mg 단결정에서는 5 mol% 이상의 MgO 첨가시 Mg가 Nb 자리를 차지하여$Mg_{Nb}^{2+}$를 형성함에 따라 광손상에 대한 저항이 크게 향상될 수 있다. 실제로 융액에 5 mol% 이상의 MgO 첨가시)$LiNbO_3$ : Mg 단결정의 광손상 저항이 3배 이상 향상되었다.

• 한국결정성장학회지
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• 제12권1호
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• pp.50-55
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• 2002

$LiNbO_3$ 단결정에 $Nd_2O_3$0.2~0.5 wt.%를 칭량하여 결정을 성장 시켰다. 그리고 광손상을 억제하기 위해 ZnO 2~8 mole%를 첨가하여 광손상에 대한 저항성을 높였다. 본 연구에서는 Nd가 doping된 단결정을 성장시켜 주기적인 domain을 만들고자 하였다